The present invention relates to adjusting devices and, in particular, to a clutching headlamp adjuster used to change the horizontal and vertical aim of motor vehicle headlamps.
The aim of a headlamp in a motor vehicle must be set to meet certain specifications, first in a factory setting, and thereafter at specific time intervals by means of adjustment. Special adjustment devices exist which provide adjustment of the horizontal and vertical setting of a headlamp with respect to the headlamp housing. With such devices, the reflector of the headlamp is usually connected to the headlamp housing at three points; one point is fixed, and the other two points consist of the horizontal and vertical adjustment devices. An example of one such device, which is generally referred to as a xe2x80x9cright-anglexe2x80x9d adjuster is disclosed in U.S. Pat. No. 5,707,133 to Burton.
Another type of adjuster is disclosed in U.S. Pat. No. 6,036,341 to Dobler et al. These adjustment devices generally consist of a threaded setting screw connected to the headlamp housing along the axis of rotation. This setting screw is fixed axially, but allowed to rotate. Further, the setting screw has a crown wheel with bevel-wheel toothing for engaging a drive, and is attached to a guide part which can move along the axis of the setting screw when the setting screw rotates. This guide part is also connected to the reflector via connecting elements, e.g., a socket. Thus, when the setting screw is rotated by means of the drive, the reflector moves in the corresponding direction of adjustment. At the same time, depending on the direction of rotation, the orientation of the reflector within the headlamp housing changes.
The setting screw is driven by a bevel gear that engages the bevel-wheel toothing on the crown wheel. The bevel gear is attached to the headlamp housing so that it can rotate, and is driven with the aid of a drive means, such as a screwdriver, which engages into a corresponding recess of the bevel wheel. The bevel gear transmits the torque to the crown wheel, with the result that the setting screw rotates about its longitudinal axis to move the guide part.
This adjustment system works well when the bevel wheel is not driven past the systems end position. However, going beyond the end position can result in damage to the adjustment device, the reflector, or the headlamp housing. Specifically, when built-in fixed stops are used, the device moves up against a stop so that when the driving bevel wheel is rotated further, damage to the weakest point of the device may occur. For example, the drive may slip, the setting screw may fracture, or the adjusting thread may slip. If there is no fixed stop provided in the device, the setting screw may become unscrewed from the counterthread of the guide part. As a result, the reflector and guide part fall out of the headlamp housing.
Alternatively, some adjusting devices use a spring instead of a fixed stop. If a setting screw loosens from the device, the spring presses the thread of the setting screw back into the counterthread of the guide part. However, one disadvantage of this spring setting device is that the setting screw and the guide part may reach an end position in which only a very short portion of thread remains with which to withstand all the torque. In this case, the threads may be stripped off.
In all the above mentioned adjustment devices, failure can occur so that the headlamp is useless. Unfortunately, a motor vehicle headlamp is only available as a part of an entire headlamp assembly. Therefore, replacement of the headlamp unit is significant expense for the car owner.
Thus, there is a need for an adjustment device that cannot be over adjusted. The present invention will be better understood from the following detailed description of the invention, read in connection with the drawings as hereinafter described.
The present invention provides a mechanism for a device used to set the distance between a first component and a second component, such as that used in a headlamp assembly, that will not break due to over adjustment. The mechanism is lightweight, non-corrosive, robust, and reliable and overcomes the disadvantages of the prior art.
As described in more detail below and shown in the accompanying drawings, the adjustment device includes a mechanism that prevents continued adjustment in the same direction once a maximum torque has been applied thereto, so that the adjustment device will not break upon application of additional torque. This is accomplished with a slipping clutch that fails to transmit torque to the adjustment device once the maximum torque has been applied. One or more of the following embodiments may be best suited for use in a particular application ranging from automobile headlamp adjusters to clocks and toys.
In one embodiment of the present invention, the slipping clutch is used as part of a mechanism to adjust the distance between a first component and a second component. In general, the slipping clutch includes a first clutch part adapted for engagement with a crown wheel. The crown wheel can be part of the second component, or on an intermediate component between the second component and the slipping clutch. The slipping clutch is generally constructed from a first clutch part and a second clutch part. The second clutch part is connected to the first clutch part so that it can rotate with respect thereto after a maximum torque has been applied to the slipping clutch. The xe2x80x9cslippingxe2x80x9d or rotation after the maximum torque has been reached prevents any additional adjustment between the first and second components, and thereby prevents breakage of the adjustment device.
The slipping clutch is substantially cylindrical, and further includes a bevel wheel at one end of the first clutch part, and a connecting head or a cavity at its opposite end. The second clutch part is connected to the first clutch part so that it cannot move axially with respect thereto, and the second clutch part can only move rotationally with respect to the first clutch part once the maximum torque has been applied to the slipping clutch. Therefore, the second clutch part includes a complementary cavity or connecting head for attachment with the cavity or connecting head of the first clutch part.
A plate is coupled between the first clutch part and the second clutch part, and has at least one boss protruding therefrom, or alternatively, and indent therein. The boss(es) or indent(s) on the plate are aligned with complementary boss(es) or indent(s) located on the first or second clutch part. When the first and second clutch part are attached together, the boss(es) fit into their corresponding indent(s) and stay there until the maximum torque causes the boss(es) to become unseated with respect to the indent(s) to and allow the first clutch part to be rotatable with respect to the second clutch part.
In another embodiment of the present invention, the slipping clutch is in combination with a device for setting the distance between a first component and a second component. Such devices generally include a setting screw adapted for connection to the first component, and a guide part connected to the setting screw and adapted for connection to the second component. The slipping clutch engages the setting screw in a manner that causes the guide part to move axially with respect to the setting screw until a maximum torque is applied to the slipping clutch.
Another embodiment is a method for producing a plastic slipping clutch having a first clutch part and a second clutch part. The method includes forming the first clutch part from a first plastic in a first mold, and forming the second clutch part from a second plastic in a second mold, wherein the shape of the first clutch part is at least part of the second mold.
The present invention can be used with any number of headlamp adjusters, such as those disclosed in U.S. Pat. Nos. 5,707,133; 5,214,971; and 6,050,712, to Burton the disclosures of which are incorporated herein by reference, and U.S. Pat. No. 6,036,341 to Dobler. As such, the term xe2x80x9cadjusterxe2x80x9d and variations thereof used herein should be interpreted as being inclusive of any of the wide variety of adjustment devices possible, including, without limitation, a wide variety of headlamp adjusters.
In sum, the present invention represents a significant improvement over the prior art in many ways. These and other objects and advantages of the present invention will become apparent from the detailed description and accompanying drawings.